Systems and methods for wound protection and exudate management

ABSTRACT

The present invention provides systems and methods for protecting a wound and managing exudate released from the wound comprising a dressing having a support cushion for surrounding the wound and periwound region; a wicking strip for application in the periwound region between the support cushion and the wound; and a reservoir for application over the wicking strip, the wicking strip configured to transfer exudate from the wound to the reservoir, where the exudate is sequestered. Various alternative embodiments are described in which the wicking strip may be custom-fit to approximate an irregular wound margin, to apply a preferred pressure gradient to the periwound regions, to periodically apply fluids to the wound bed or to apply negative pressure wound therapy. Methods of applying the dressing also are provided.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 12/416,826, filed Apr. 1, 2009 now U.S. Pat. No.8,067,662 and entitled “Systems and Methods for Wound Protection andExudate Management,” the entire contents of which are incorporated byreference herein.

II. FIELD OF THE INVENTION

This application generally relates to systems and methods for promotingthe healing of wounds, and particularly to systems and methods forpromoting the healing of wounds that generate exudate.

III. BACKGROUND OF THE INVENTION

Wounds occur when the integrity of tissue is compromised, affecting oneor more layers of the epidermis or underlying tissue. Acute wounds maybe caused by an initiating event, such as a accident-related injury,surgical procedure or by operation of an infectious disease, andgenerally take the form of punctures, abrasions, cuts, lacerations, orburns. Chronic wounds are wounds that generally do not heal within threemonths, due to one or more of: ischemia of the vessels supplying thetissue, venous hypertension or compromise of the immune response, suchas observed, for example, with venous ulcers, diabetic ulcers andpressure ulcers. Depending on etiology, such as diabetes, venousinsufficiency, or cardiovascular failures, acute wounds may becomerecalcitrant and even chronic.

The introduction of bacteria from external sources into the woundtypically causes inflammation that activates the patient's immuneresponse, in turn causing white blood cells, including neutrophilgranulocytes, to migrate towards the source of inflammation. While theyfight pathogens, such neutrophils also release inflammatory cytokinesand enzymes that damage cells. In particular, the neutrophils produce anenzyme called myeloperoxidase that in turn is metabolized to producereactive oxygen species that kill bacteria. Collaterally, such enzymesand reactive oxygen species damage cells in the margin surrounding thewound, referred to as the “periwound,” thereby preventing cellproliferation and wound closure by damaging DNA, lipids, proteins, theextracellular matrix and cytokines that facilitate healing. Becauseneutrophils remain in chronic wounds for longer than in acute wounds,they contribute to higher levels of inflammation. Moreover, thepersisting inflammatory phase in chronic wounds contributes to exudate(fluid that flows from the wound) with high concentrations of matrixmetalloproteases (MMPs). Excess MMPs results in degradation ofextracellular matrix protein. In addition to damaging the wound, exudatedamages the periwound tissue exposed to it as well. In particular,exudate that flows out of the wound and onto periwound region may damagethe fragile skin, which is already compromised due to the patientsunderlying etiology, such as diabetes. Such damage may degrade theperiwound skin and cause its breakdown and turn it into a wound. Thus,exudate flow onto the periwound region will cause many complications,including, the potential for increasing the size of the wound andprolonging its healing. Such damage to the skin in the periwound region(periwound skin) makes it more susceptible to tearing and resultantintense pain as dressings or devices adhered to them are removed. Othercomplications include infection of the periwound region and intenseitching.

Patients suffering from chronic wounds frequently report experiencingsevere and persistent pain associated with such wounds, which may arisefrom necrosis of and/or nerve damage of the skin and underlying tissue.Treatment for such pain often consists of low dose analgesics, whiletopical antibiotics and/or debridement, which seeks to remove necrotictissue from the wound, may be used to control the bacterial load at thewound site.

Conventional wound treatment also typically involves covering the woundwith a dressing to prevent further contamination and infection, toretain moisture, and to absorb exudate. While exudate containsbiochemical compounds that benefit wound healing as noted above, itsexcessive amount in wound or its presence in the periwound regionfacilitates degradation of tissue, and the exudate additionally servesas a growth medium for bacteria. The consistency of exudate varies,depending on the type of wound and the stage of healing. For example,exudate may be watery, extremely viscous, or somewhere in between.Moreover, the sizes of wounds can vary greatly, as can their care.

Although a wide variety of dressings have been developed, fewpreviously-known wound treatment systems properly manage exudate, e.g.,removing a sufficient amount of exudate from the wound site, whileprotecting the periwound region from damaging contact with the exudate.Moreover, conventional systems typically do not address the pain createdby the wound treatment system, particularly where the wound treatmentsystem continuously contacts the wound. For example, gauze, which isapplied directly onto a wound, is capable of absorbing only a limitedamount of exudate, and readily transports excess exudate onto theperiwound region, causing maceration and damage. Moreover, the gauzetypically is in direct contact with the wound and adheres to it, so thatnormal motion of the patient results in rubbing, itching and discomfort.In addition, removal of the gauze at periodic intervals is painful andfrequently disrupts any healing that may have occurred.

Some previously-known approaches to wound treatment attempt to reduceadhesion between the wound and the dressing by applying additionalsubstances. For example, the wound and dressing may be soaked in salinewater to loosen adherence and/or soften any scabs that formed, thusfacilitating removal of the dressing. Or, for example, antibioticointments such as polymyxin B sulfate or bacitracin can be applied toreduce sticking. However, such methods are not always satisfactorybecause soaking a particular wound in water or applying ointments maynot be practicable or recommended.

Some previously-known dressings are promoted as being “non-stick” or“non-adherent,” such as TELFA™ and XEROFORM™, and other brands that maybe composed of materials such as hydrocolloids, alginates, andhydrofilms. Regardless of the level of adherence of such dressings tothe wound, continuous contact between the dressing and wound disturbsthe fragile wound matrix, and may undermine the growth of blood vesselsand epithelial cells in the wound bed. Such disturbance often occurswhen the dressing is removed, or simply as a result of the contactbetween the bandaged area and the patient's environment. Pain is oftenconcomitant with such disturbances. In addition, previously-known“non-stick” dressings usually do not absorb sufficient amounts ofexudate, and thus require frequent monitoring and changing. Thesedrawbacks add to the cost of use and limit the applicability of suchpreviously-known wound treatment systems.

Previously-known dressings commonly have only a limited ability tomanage wound exudate. As noted above, prolonged exposure of otherwisehealthy skin to exudate may cause degradation of the periwound region.The moisture of the exudate may cause maceration, which is a softeningof the skin that compromises its integrity and makes the skin in theperiwound region vulnerable to physical insult and infection.

Some previously-known dressings attempt to manage exudate to address theforegoing issues, but provide either limited benefit and/or at a muchhigher perceived cost. For example, a foam dressing such as ALLEVYN®(marketed by Smith & Nephew, Largo, Fla., USA) is designed to absorblarge amounts of exudate. However, use of this product is restricted tohighly exuding wounds, because its highly absorptive properties canresult in desiccation of wounds that are not highly exuding, therebyimpeding healing. In addition, because foam used in that product cannotbe conformed to the size and shape of the wound, the dressing typicallyoverlaps with the periwound region. Consequently, exudate absorbed bythe foam is transported throughout the foam and onto the periwoundregion, where prolonged exposure leads to maceration and degradation ofthe periwound region. Other previously-known dressings, such asACQUACEL® hydrofiber dressing (available from ConvaTec, Inc., Princeton,N.J., USA) contact the wound bed, and are intended to absorb exudate andtransfer and sequester the exudate in a layer disposed atop the wound.This and similar previously-known dressings do not entirely contain orabsorb exudate. Moreover, like foam and other previously-knowndressings, hydrofiber dressings essentially plug the wound surface, andcreate an osmotic environment in which the fluidic osmotic pressurewithin the wound bed approximates that of the surrounding tissue.Consequently, exudate is not sufficiently drawn from the wound, and itsbuildup in the wound may adversely affect the wound and periwoundregion. Furthermore, ALLEVYN®, ACQUACEL®, and similar previously-knowndressings do not provide an adequate moisture vapor transfer rate (MVTR)away from the wound environment, thus creating the potential for anover-hydrated environment that hinders wound healing.

Other previously-known wound treatment systems, such as the V.A.C.®system, available from Kinetic Concepts, Inc. (San Antonio, Tex., USA),employ a mechanically operated contact-based dressing that continuouslyvacuums exudate from the wound bed. It and other dressings incorporatingthe concept of Negative Pressure Wound Therapy have proven particularlyuseful in healing large wounds, such as surgical wounds. However, suchsystems are costly, difficult to apply and time consuming. In addition,because such systems require insertion of a sponge (for the V.A.C.®system) or gauze (as commercialized by other wound care companies)directly into the wound bed, they likely cause considerable pain anddiscomfort for the patient, and may not be appropriate for many types ofwounds.

Several previously-known dressings also have been developed that arepromoted as “non-contact” dressings, which seek to prevent adhesion ofthe wound tissue to dressing, or to facilitate certain treatments thatby their nature cannot contact the wound, e.g., thermal therapy. Suchdressings are commonly formed as an inverted cup or a raised bandagethat covers the wound without contacting it. Such previously-knowndressings, however, also have failed to adequately heal wounds andprotect the periwound region. Such non-contact dressings are provided inpre-formed shapes and sizes, and have limited deformability, thuslimiting their ability to prevent exposure of the periwound skin toexudate. Additionally, the limited deformability of suchpreviously-known dressings makes application of such dressings difficultor impossible to wounds on small surfaces or in areas with complextopology, such as the ankle or foot. Previously-known non-contactdressings also do not allow the pressure applied to the periwound regionto be readily managed, and may result in the formation of pressure ringsaround the wound, thereby inducing ischemia in the wound and surroundingtissue. Finally, such previously-known dressings do not provide anymechanism to stimulate the flow of exudate, nor do they sequesterexudate away from the wound in any appreciable volume. Suchpreviously-known dressings also trap humidity over the wound andperiwound region, leading to maceration, periwound degradation andimpeded healing.

IV. SUMMARY OF THE INVENTION

The present invention provides systems and methods for treatment ofwounds by managing exudate and cushioning wounds from external pressuresources. The dressing of the present invention may be used for a widerange of chronic wounds, including venous ulcers, diabetic foots ulcers,pressure ulcers, and arterial ulcers. In addition, dressings constructedin accordance with the present invention may be advantageously used forsurgical wounds to protect the incision site, particularly for surgicalareas where skin is most vulnerable, such as split-thickness graft sitesand cosmetic surgeries.

Dressings constructed in accordance with the present invention also mayadvantageously used to treat acute wounds and to protect the wound fromfurther trauma, such as occurs in industrial accidents and in the battlefield settings. In particular, dressings in accordance with the presentinvention may be applied to reduce contact pressure on the wound bed. Ina battlefield setting, for example, this aspect of the invention may beparticularly valuable, since a bandaged wound may still have debris orshrapnel in it, and the dressing can be applied to prevent suchcontaminants from being pushed further into the wound during evacuationof the wounded subject.

In accordance with one aspect of the present invention, a system isprovided for managing exudate released from a wound that is surroundedby a periwound region, the system including: a support cushion thatsurrounds the wound and the periwound region; a wicking strip configuredto be applied in the periwound region between the support cushion andthe margin of the wound; and a reservoir that is disposed over thewicking strip to absorb and sequester exudate from the wicking strip.The wicking strip may include a substantially hydrophobic film on thesurface that contacts the periwound region, so that exudate is absorbedthrough a lateral surface of the wicking strip exposed to the wound bed,but exudate entering the wicking strip does not contact or causemaceration of the periwound tissue located beneath the hydrophobic film.Preferably, the hydrophobic layer may also serve as an adhesive thatadheres the wicking strip to the periwound tissue at the margin of thewound.

In some embodiments, the support cushion includes a high-profile portionconfigured to accommodate the reservoir; and a low-profile portionconfigured to suspend the reservoir over the wound. The high-profile andlow-profile portions of the support cushion may be hydrophobic; thewicking strip and the reservoir may be hydrophilic; the high-profileportion may inhibit lateral flow of exudate out of the reservoir; andthe low-profile portion may inhibit lateral flow of exudate out of thewicking strip. In some embodiments, the support cushion also may includea plurality of slits to enhance conformability of the cushion to complexpatient topology, and to allow the transfer of moisture vapor from theskin on which the support cushion rests.

Some embodiments further may include a cover secured to the reservoir;and a biocompatible adhesive for securing the cover to the supportcushion, so that the adhesive urges the reservoir into engagement withthe wicking strip. The wicking strip may have a length and a height,such that the height varies along the length to modulate or provide agradient in the pressure applied to the periwound region. Abiocompatible adhesive may secure the support cushion around the woundand the periwound region; and a biocompatible adhesive may secure thewicking strip in the periwound region between the wound and the supportcushion.

In some embodiments, the reservoir may include a first hydrophiliclayer, a non-stretchable mesh or scrim, and a second hydrophilic layer.In other embodiments, the reservoir may include a vent or vents thatcontrol humidity over the wound. Further, the reservoir or supportcushion may include a port or ports for applying negative pressurewithin the dressing to provide negative pressure wound therapy, orthrough which a lavage solution may be periodically injected andwithdrawn.

In accordance with another aspect of the invention, a method formanaging exudate from a wound surrounded by a periwound region isprovided, and includes: surrounding the wound and the periwound regionwith a support cushion; applying a wicking strip in the periwound regionbetween the support cushion and the wound; and applying a reservoir overthe wicking strip, wherein the wicking strip transfers exudate from thewound to the reservoir. In some embodiments, the method includessubstantially filling the periwound region between the support cushionand the wound with the wicking strip.

In other methods of the present invention, the support cushion mayinclude a vertically profiled portion, with the method further includingfitting the reservoir within the profiled portion of the support cushionto suspend the reservoir over the wound. In such embodiments, thesupport cushion may be hydrophobic and the wicking strip and thereservoir may be hydrophilic, or optionally a combination of hydrophobicand hydrophilic materials, the method further including inhibitinglateral flow of exudate out of the reservoir and the wicking strip.

Still other methods of the present invention are designed to stimulateexudate flow by arranging the reservoir to compress the wicking strip,thereby applying a mild pressure in the periwound region that encouragesexudate to migrate out of the wound and into the wicking strip. Thewicking strip also may have a length and a height that varies along thelength, such that the variation in height induces a pressure gradient inthe periwound region when the reservoir is urged into engagement withthe wicking strip. In some methods, the pressure gradient may be inducedby applying a compression wrap over the dressing. A medication may beapplied to the wound before applying the reservoir.

In still other embodiments, the method further may secure a cover to thesupport cushion with a biocompatible adhesive so that the adhesive urgesthe reservoir into engagement with the wicking strip. The method mayfurther include securing the support cushion around the wound and theperiwound region with a biocompatible adhesive; and securing the wickingstrip in the periwound region between the wound and the support cushionwith a biocompatible adhesive.

In accordance with yet another aspect of the present invention, a kitfor use in managing exudate from a wound surrounded by a periwoundregion is provided and includes: a support cushion for surrounding thewound and the periwound region; a wicking strip configured to be appliedin the periwound region between the support cushion and the margin ofthe wound; a reservoir configured to be applied over, and in engagementwith, the wicking strip; a backing upon which the support cushion,wicking strip, and reservoir are mounted; and printed instructions forusing the support cushion, wicking strip, and reservoir on a patient.

V. BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B and are an exploded view and a cross-sectional view,respectively, of an exemplary dressing of the present invention, whileFIG. 1C is a partial sectional view illustrating transfer of exudatefrom the wound to the reservoir via the wicking strip.

FIG. 2 illustrates steps in accordance with one method of the presentinvention for exudate management.

FIG. 3 illustrates a perspective view of an illustrative application ofthe inventive dressing of FIG. 1 to a patient.

FIG. 4 schematically illustrates a plan view of one preferred embodimentof the support cushion and wicking strip.

FIGS. 5A-5C illustrate alternative embodiments of a wicking stripsuitable for use in the exudate management system of the invention.

FIGS. 6A-6B illustrate further alternative embodiments of a wickingstrip suitable for use in the exudate management system of theinvention.

FIG. 7 schematically illustrates a plan view of a reservoir, cover, andoptional vent according to some embodiments of the invention.

FIG. 8 is a plan view of an alternative embodiment of the supportcushion and wicking strip of the present invention.

FIG. 9 is a plan view of another alternative embodiment of the supportcushion and wicking strip of the present invention.

FIG. 10 is a perspective view of an alternative embodiment of theexudate management system of the invention including a lavage system, inwhich the wicking strip has been omitted for improved clarity.

FIG. 11 is a perspective view of another alternative embodiment of theexudate management system of the invention including a manually-operatedbellows for applying a negative pressure within the dressing.

FIGS. 12A and 12B are an exploded view, and a partial sectional view,respectively of another alternative embodiment of the dressing of thepresent invention.

FIGS. 13A and 13B are a plan view and perspective view, respectively, ofan alternative embodiment of a cover and reservoir constructed inaccordance with one aspect of the present invention.

FIG. 14 schematically illustrates a plan view of a kit containing asystem for exudate management, according to some embodiments of theinvention.

VI. DETAILED DESCRIPTION OF THE INVENTION

The present invention provides systems and methods for protecting andpromoting wound healing by managing exudate released by the wound. Amongother things, the systems and methods provide a wound dressing thatallows a wound to remain moist, while at the same time transferringexcess exudate away from the wound and periwound region to a separatelylocated reservoir. In this manner, the wound does not come intoprolonged contact with excess exudate and periwound will not come incontact with any exudate, and thus both are protected from maceration orbacterial action that degrades tissue and skin. Unlike previously-knowndressings, a dressing constructed in accordance with the principles ofthe present invention includes a reservoir that is elevated above thewound, and thus does not continuously contact the wound. Thisarrangement promotes wound healing by reducing the disruption of thewound bed (and pain) caused by periodic replacement of previously-knowndressings, such as gauze, which adhere to the wound bed.

The systems and methods of the present invention also allow the flow ofexudate from the wound to be managed by manipulating the amount andprofile of pressure applied to the periwound skin, which also isexpected to enhance the rate of healing of the wound.

An overview of an exemplary embodiment of a system for exudatemanagement constructed in accordance with the principles of the presentinvention is first described, as well as a method of applying and usingthat system. Further details on the individual components employed inthe system of the present invention, and alternative embodiments andmethods, are described.

Overview of System

Referring now to FIGS. 1A and 1B, an exemplary embodiment of wounddressing 10, constructed in accordance with the principles of thepresent invention to provide exudate management, is described. In thisexemplary embodiment, dressing 10 comprises three discrete componentsthat are assembled and applied by the patient, nurse, clinician or othercaregiver over wound W in patient's epidermis E. In particular, dressing10 includes support cushion 20, wicking strip 30, and reservoir 40,preferably pre-attached to cover 50. Preferably, components 20, 30, 40and 50 of dressing 10 are sized for use with one another and areenclosed in a sterile package with suitable instructions to enable thepatient or caregiver to quickly and accurately apply the dressing.Alternatively, because for some embodiments certain components ofdressing 10, such as wicking strip 30 and/or reservoir 40, may bereplaced on a frequent basis than other portions of the dressing, suchcomponents may be individually packaged.

Support cushion 20 preferably comprises a closed cell polyolefin foamand is designed to surround wound W and periwound region P, i.e., theregion of epidermis E extending from the wound margin, to protect thewound and elevate reservoir 40 and cover 50 above the wound bed. In theexemplary embodiment of FIG. 1, support cushion 20 has a steppedprofile, including sidewall 21 and flange 22. The upper surface offlange 22 forms ledge 23 that supports reservoir 40, as depicted in FIG.1B. Lower surface 24 of support cushion 20 includes layer 25 ofbiocompatible adhesive, which preferably is hydrophobic and breathable,while upper surface 26 includes layer 27 of adhesive or a portion of areusable fastening system, e.g., the pile of a hook and pile fasteningsystem, such as Velcro. Use of a non-permanent adhesive for layer 27permits the cover to be removed to periodically replace wicking strip 30and/or reservoir 40, as described below. In addition, support cushion 20preferably includes slits or perforations 28 that extend through theheights of sidewall 21 and flange 22 to facilitate the escape ofperspiration from beneath support cushion 20 when is it fastened bylayer 25 to epidermis E. Support cushion 20 includes opening 29 thatexposes a portion of the periwound region P extending away from themargin of wound W, to permit placement of wicking strip 30, as depictedin FIG. 1B.

Wicking strip 30, which preferably comprises an open-cell polyurethanefoam, overlays periwound region P between the margin of wound W andflange 22 of support cushion 20. In the embodiment of FIG. 1, wickingstrip 30 is depicted as a curved strip of foam, although it takes otherforms as described herein for alternative embodiments. Wicking strip 30preferably includes layer 31 of biocompatible adhesive, which preferablyis hydrophobic and breathable, on lower surface 32. During application,wicking strip 30 may be rolled to a tighter spiral than depicted in FIG.1A that it fits snugly within opening 29 of support cushion 20 and theinnermost edge of the wicking strip preferably overlaps the margin ofthe wound by 1-2 mm. For the embodiment of FIG. 1A, wicking strip 30 maybe cut with a scissor to ensure that the foam is not overly compressedwhen adhered to the periwound region by layer 31. In a preferredembodiment, establishing snug contact between the outermost edge ofwicking strip 30 and the inner-facing surface of flange 22 ensures thatexudate does not leak onto an exposed portion of the periwound regionbetween wicking strip 30 and support cushion 20. Alternatively,outer-facing surface 32 of wicking strip 30 may employ a hydrophobicfilm or coating that prevents exudate from seeping into the periwoundregion.

Still referring to FIG. 1, reservoir 40 preferably comprises a sandwichof different density open cell polyurethane foams 41 and 42 joined tomesh 43, in which the foams 41 and 42 are selected to absorb exudatefrom wicking strip 30 and to sequester the exudate away from the woundbed. In the embodiment depicted in FIG. 1, reservoir 40 is fastened tothe underside of cover 50, and is sized so that the outer edges of thereservoir are supported on ledge 23 of support cushion 20, while themore central regions of the reservoir engage the upper surface ofwicking strip 30. Preferably, reservoir 40 fits within sidewall 21 ofsupport cushion 20, so that exudate drawn into the reservoir fromwicking strip 30 cannot seep out of the lateral face of the reservoir.As shown in FIG. 1B, flange 22 suspends reservoir 40 over wound W, thusinhibiting contact between reservoir 40 and wound W and limiting theextent to which force applied to cover 50 and reservoir 40 istransmitted to wicking strip 30. Wicking strip 30 may additionallysupport reservoir 40 over wound W. Optionally, a layer of adhesive maybe disposed on the lower surface of the reservoir 40 that engages ledge23 of the support cushion to removably secure those components together.Reservoir 40 preferably includes one or more vents 44 that assist inmodulating the humidity within the dressing through cover 50.

Cover 50, preferably a breathable material, overlays reservoir 40. Layer51 of adhesive preferably is used to removably secure reservoir 40 tocover 50. Alternatively, reservoir 40 may be removably fastened to cover50 using a removable fastening system, such as hook and pilearrangement. In addition, layer 27 of adhesive, or a removable fasteningsystem, is used to secure cover 50 to the upper surface of sidewall 21of support cushion 20, so that cover 50 and/or reservoir 40 may beperiodically removed from dressing 10 to inspect the wound, to applytopical medications or other substances to the wound, e.g., moisturizingointments, growth factors, nutrients, and/or antibiotics, or to replacewicking strip 30 or reservoir 40. In other embodiments, cover 50 and/orreservoir 40 are left in place over the wound while dressing 10 isapplied to the patient.

As described in greater detail below, the components of dressing 10 mayeach be provided with one or more non-stick liners to facilitatehandling of the different components of the system, e.g., while placingsupport cushion 20 on epidermis E. The liners may be removed asappropriate to expose the adhesive layers and secure components toepidermis E or to each other.

Referring now to FIGS. 1B and 1C, during use of dressing 10, exudate EXflows out of wound W at a flow rate that depends on many factors,including the pressure with which wicking strip 30 is pressed againstthe periwound region, the lateral profile of wicking strip 30 (describedin greater detail below with reference to FIGS. 5A-5C), thecharacteristics of wound W, and the consistency of the exudate. Asexudate EX is released from the wound, some of the exudate pools on topof wound W. As discussed above, such accumulation of excess exudate withhigh concentrations of MMPs leads to degradation of extracellular matrixprotein both in the wound and on periwound skin. However, excess exudatemay flow from the wound, or gravity and/or patient movement may displaceexudate from the wound bed so that it contacts and is absorbed bywicking strip 30.

As depicted in FIG. 1C (from which cover 50 has been omitted forclarity), wicking strip 30 transports exudate EX laterally (in the planeof epidermis E) and then vertically (perpendicular to the plane ofepidermis E) to reservoir 40. Specifically, the exudate travels along agradient from relatively wet regions to relative dry regions of thewicking strip via capillary action. Exudate transported laterally mayeventually reach the inner surface of flange 22 of support cushion 20.Because support cushion 20 is formed of a hydrophobic material, itinhibits further lateral transport of the exudate. Instead, exudatepreferably is transported vertically from wicking strip 30 and intoreservoir 40, which sequesters exudate away from the wound. Inaccordance with one aspect of the invention, reservoir 40 preferably hasa large absorptive surface area and the capacity to hold large amountsof exudate, e.g., sufficient capacity so that reservoir 40 need only bereplaced once every few days (for example, every 7-10 days). Reservoir40 is also breathable, so that it releases water in the exudate in theform of vapor V into the atmosphere via breathable cover 50.Additionally, ledge 23, upon which reservoir 40 rests, and sidewall 21,adjacent to reservoir 40, are hydrophobic and cannot transfer exudatefrom reservoir 40 onto the periwound region. Accordingly, dressing 10 isconfigured to inhibit prolonged contact between the exudate andperiwound region, and thus to inhibit maceration or other degradation ofthe periwound region, as observed with previously-known dressings.

Multiple features of dressing 10 both enhance the healing of wound W andprotect periwound region P from maceration and degradation. Among otherthings, although reservoir 40 is arranged to protect the wound from theenvironment and absorb exudate, it is suspended over and thus is not incontinuous contact with the wound. This feature may both reduce any painexperienced by the patient and promote healing. For example, initiallyplacing reservoir 40 (and the other components of dressing 10) does notrequire touching the wound bed itself, resulting in significantly lesspain than, for example, than the V.A.C.® or systems similar to itdescribed above that rely on inserting a sponge or gauze directly intothe wound. Wicking strip 30 and/or reservoir 40 also may readily beremoved without disrupting re-epithelialization of the wound. Moreover,because reservoir 40 sequesters the exudate, when reservoir 40 isremoved to observe the wound, exudate does not flow onto the adhesiveused to secure cover 50 to support cushion 20. This arrangement allowswicking strip 30 and/or reservoir 40 to be replaced and for cover 50 tobe re-secured to support cushion 20, without having to replace theentire dressing. By contrast, removing previously known dressings (whichcontact the wound) often disrupts re-epithelialization and allow exudateto flow onto the adhesive, requiring the entire wrap to be discarded anda new one applied.

It is noted that although reservoir 40 is designed to be suspended over,rather than in contact with the wound, occasions may arise where thereservoir will contact the wound. For example, if sufficient pressure isapplied directly onto cover 50 and reservoir 40, the reservoir maydeflect sufficiently to contact the wound for as long as that pressureis applied. Such temporary contact is not believed to significantlyimpede the healing of the wound, and the durometer and resiliency ofsupport cushion 20 preferably is selected to provide adequate supportfor cover 50 and reservoir 40 in the expected range of applications.

Dressing 10 also encourages the flow of exudate from the wound, and thusreduces the bacterial load of the exudate in contact with the wound bed.Without wishing to be limited by theory, the inventors believe that theflow of exudate from the wound may stimulate healing. First, dressing 10encourages exudate flow by continuously wicking exudate out of thewound, thereby providing a lower osmotic pressure at the wound than inthe surrounding tissue. This osmotic pressure differential encouragesexudate to flow from the surrounding tissue into the wound to attempt toequalize the osmotic pressure. In contrast, conventional dressings thatdirectly contact the wound typically do not generate an osmotic pressuredifferential. In addition, because dressing 10 absorbs exudate from thewound and promotes replenishment of exudate, the bacterial load of theexudate in contact with the wound bed remains relatively low. Dressing10 also is configured to allow a variety of different types of pressureto be applied to the periwound region, depending on the type of wound,as described in greater detail below with respect to FIGS. 5A-5C.

Additionally, dressing 10 is well-suited for use in treating pressuresores that may be acquired by patients whose skin may be damaged by, forexample, continuously lying in bed without sufficient movement. Suchpressure sores may occur where skin is thin, has reduced integrity,and/or where bone and skin are close together, without sufficientintervening muscle or fat. Support cushion 20 rests on regions ofepidermis E that surround the wound, thus protecting the wound from thetype of pressure that initially caused the wound. Support cushion 20 maybe formed of a supple, easily bendable material that does not create apressure ring around the wound. In some embodiments, support cushion 20is formed of a polyolefin that distributes pressure, inhibiting thatpressure from concentrating in one region.

Overview of Method

FIG. 2 illustrates steps in a method 60 of using dressing 10 formanaging exudate from a wound, according to some embodiments of theinvention. Typically, the method is implemented by a physician, nurse,or other caregiver. However, the method is relatively simple to employ,and the patient himself may apply dressing 10.

First, at step 61, the caregiver obtains support cushion 20, wickingstrip 30, reservoir 40, and cover 50, e.g., a kit as described belowwith respect to FIG. 7. Next, in step 62, support cushion 20 is appliedto the epidermis of a patient, so that the support cushion surrounds thewound and periwound region. For example, a non-stick liner coveringlower surface 24 of support cushion 20 may be removed to expose theadhesive on its lower surface. The support cushion then is roughlycentered around the wound, and pressed onto the patient's epidermisusing gentle manual pressure. A non-stick liner covering layer 27 on theupper surface of support cushion 20 may be left in place until a laterstep, described below.

At step 63, wicking strip 30 is applied within the periwound regionbetween the margin of the wound and support cushion 20. For example,wicking strip 30 will include a non-stick liner covering layer 31, andthis liner will be removed to expose the adhesive. A first end ofwicking strip 30 then is applied and adhered to a first portion of theperiwound region, e.g., just overlapping the margin of the wound. Thefree end of the wicking strip then is spiraled around the wound, withsubsequent portions of wicking strip 30 adhered to adjacent portions ofthe periwound region, for example, as illustrated in FIG. 4, until theentirety of the periwound region exposed within opening 29 of thesupport cushion is filled. Preferably, wicking strip 30 fillssubstantially the entire periwound region between the wound and supportcushion 20, to prevent seepage of exudate from the outermost lateralface of the wicking strip. In some circumstances, the wound may besufficiently large that the entire wicking strip 30 is not needed tofill the periwound region between the wound and support cushion 20, inwhich case wicking strip 30 may be cut to the appropriate length. Thewound may have a relatively irregular shape, and simply spiralingwicking strip 30 around the wound will adequately fill the entireperiwound region. Alternatively, wicking strip 30 may be cut intomultiple pieces of appropriate lengths, which are individually adheredto the periwound region as appropriate.

At step 64, reservoir 40 and cover 50 (which is preferably pre-adheredto reservoir 40) then are applied over wicking strip 30. For example,the non-stick liner may be removed from layer 27 disposed on the uppersurface of side wall 21, and reservoir 40 inserted into support cushion20 so that the exposed adhesive on support cushion 20 adheres to cover50, as illustrated in FIG. 1B.

At step 65, compression wrap 70 optionally is wrapped over dressing 10to apply a desired pressure onto the dressing and wound, e.g., asillustrated in FIG. 3. For example, as discussed above, the amount ofapplied pressure may affect the flow of exudate and the rate of healingof the wound, so the physician may elect to compress dressing 10. Theappropriate amount of pressure and wrap type may differ from wound towound, and may be selected based on the physician's knowledge andexperience with particular wound types. Elastic compression wraps suchas PROFORE® (Smith & Nephew, Largo, Fla., USA) may suitably be used.

For example, if using an elastic compression wrap to compress dressing10 against a venous leg ulcer, the wrap may be stretched beyond aspecified proportion of its native length, and then secured in thatstretched configuration. The physician optionally may apply other wrapson dressing 10, such as gauze or Unna Boot or both. Such interveninglayers of material also may be applied with compression, as appropriate.

Some wound sites located on broad surfaces, such as the torso, may noteasily be wrapped with a compression wrap, in which case thedifferential heights between the support cushion, reservoir and wickingstrip of dressing 10 may be adjusted to provide sufficient pressure tostimulate the flow of exudate. For example, as described herein afterwith respect to the embodiment of FIGS. 5A to 5C, a wicking strip havinga variable height may be employed with the dressing of the presentinvention. Depending upon how the wicking strip is applied surroundingthe wound, the dressing and compression wrap, if present, may beadjusted to provider either greater or lesser pressure on the tissuesurrounding the wound, or to provide a uniform pressure at the woundsite in view of complex limb topology.

Optionally, a medication or other substance may be applied to the woundor periwound region during any appropriate step in method 60. Forexample, the wound and periwound region may be cleaned, dried, and/ordebrided or moisturized before applying support cushion 20 to theepidermis. Or, for example, a wound dressing such as PROMOGRAN PRISMA™collagen and silver dressing (available from Systagenix WoundManagement, London, UK), or Dermagraft® (available from AdvancedBioHealing, La Jolla, Calif., USA), or Apligraf® (available fromOrganogenesis, Inc., Canton, Mass., USA), and other similar collagen orbiological dressings, may be applied to the wound after applying wickingstrip 30, but before applying reservoir 40 and cover 50. Othersubstances may be used, such as time-release topical medicines.

Further details of the construction of the individual components ofdressing 10, and alternative embodiments, are now provided.

Support Cushion 20

Referring to FIG. 4, support cushion 20 and wicking strip 30 are furtherdescribed. Support cushion 20 includes sidewall 21 and flange 22, whichforms ledge 23. Each of sidewall 21 and flange 22 includes plurality ofslits 28 that enhances its breathability and flexibility. In particular,slits 28 may be arranged radial or circumferential directions, or withanother preferred orientation to improve conformability of the supportcushion to the anatomy of a specific limb. Support cushion 20 preferablyis secured to patient's epidermis using a biocompatible adhesive layer,which is preferably hydrophobic but breathable, or alternatively, may besecured using a compression wrap that overlays the dressing.

In some embodiments, support cushion 20 is of unitary construction, withsidewall 21 and flange 22 being formed from different portions of thesame piece of material. Alternatively, sidewall 21 and flange 22 may beindividually constructed and then heat-fused or adhesively bondedtogether, thus allowing the materials, thicknesses, and othercharacteristics of sidewall 21 and flange 22 to be selected tailored forspecific applications. For example, it may be preferable to formsidewall 21 using a relatively thick layer of a large-cell hydrophobicmaterial and flange 22 using a relatively thin layer of a small-cellhydrophobic material. Such a combination of materials and thicknessesimparts support cushion 20 with sufficient flexibility to be conformableto substantially any body part, e.g., an arm, leg, neck, or torso, whilemaintaining a sufficient level of hydrophobicity to prevent exudate fromleaking onto the periwound region. Examples of suitable hydrophobicmaterials for use in support cushion 20 include polyolefin, foams, andsilicone-based materials, in open cell or closed cell forms. Anysuitable adhesive or bonding procedure can be used to adhere sidewall 21to flange 22.

As mentioned above, slits 28 may enhance the flexibility andbreathability of support cushion 20, e.g., to allow support cushion 20to more readily conform to various body parts and to allow humidity inthe regions of the epidermis underlying support cushion 20 to escape,thus reducing maceration. Slits 28 may be simple “cuts” that extendthrough support cushion 20, e.g., through sidewall 21 and flange 22,without removing material. Alternatively, slits 28 may be aperturesformed by removing material from sidewall 21 and/or flange 22. Slits 28may be formed in any appropriate size, shape, density, or pattern. Forexample, slits 28 may extend in a single direction, as illustrated inFIG. 4, may extend radially (perpendicular to curvature of supportcushion 20), may extend parallel to the curvature of support cushion 20,or may extend at an angle relative to the curvature of support cushion20. Some slits 28 may extend at different angles than other slits 28.

Alternatively, support cushion 20 of the present invention may comprisesa spacer fabric, such as the polyester/nylon spacer fabric designatedstyle DNB69, available from Apex Mills, Inward, N.Y., USA. Suchmaterials are hydrophobic, but include an open weave that is highlybreathable, thereby permitting moisture to readily evaporate from thepatient's skin during prolonged use, while preventing maceration.

In the embodiment illustrated in FIG. 4, support cushion 20 ispre-formed in a generally oval shape, and is suitable for use withwounds up to a fixed size, e.g., up to 30 mm in length. However, supportcushion 20 also may be formed in any other appropriate shape and sizeand may be provided having a range of size of openings 29 in flange 22.For example, support cushion 20 may be pre-formed in a generallycircular, rectangular, triangular, or other polyhedral shape, optionallyhaving rounded corners, or may even be pre-formed in an irregular shape.Alternatively, support cushion 20 may be formed as a strip that may beapplied around the wound and periwound region. The strip may be ofpredetermined length, or may even be provided on a roll and cut to adesired length. In such embodiments, it may be convenient to applysupport cushion 20 to the epidermis after wicking strip 30 is appliedaround the wound.

To accommodate such free-form embodiments of the support cushion, it maybe desirable for reservoir 40 and cover 50 to have a basket-likeconfiguration, such as described in detail below with respect to FIG.13.

In still other embodiments (not illustrated), support cushion 20 may bean annular structure filled with a fluid, e.g., air or water, a gel, anexpanded plastic, or fibers. Such structure may be formed of moldedplastic, welded polymer, or a laminate.

Wicking Strip 30

In the embodiment illustrated in FIG. 4, wicking strip 30 is anelongated strip of hydrophilic material spiraled around wound W in thespace between the wound and the inner surface of flange 22. Preferably,wicking strip 30 is sufficiently flexible that it may be applied in anydesired pattern to the epidermis, e.g., that it may be packed so as tofill substantially the entire space between the wound and the innermostsurface of defining opening 29 of support cushion 20. One example of asuitable hydrophilic, flexible material for use in wicking strip 30 isan open-cell foam such as hydrophilic polyurethane. Alternatively,wicking strip 30 may include any suitable absorbent structure, e.g., awoven fabric, a nonwoven fabric, a hydrogel (which may include modifiedstarch), or a pouch filled with a polymeric absorbent material.

In the embodiment of FIG. 1, wicking strip 30 is depicted as having thesame height as flange 22 of support cushion 20. However, wicking strip30 may actually have a different height than flange 22, but reservoir 40may compress the two components to the same height during use. Forexample, wicking strip 30 may be thicker or thinner (taller or shorter,respectively) than flange 22, and may have a different compliance. Inone embodiment, wicking strip 30 is thicker than flange 22, but is moreeasily compressed, allowing both components to be compressed to the samethickness by reservoir 40 during use.

Likewise, wicking strip 30 may have a variable width along its length,as depicted in FIG. 1A. In other embodiments, such as that depicted inFIG. 4, the width of wicking strip 30 is essentially constant along itslength. Referring to FIG. 5A, an embodiment of a wicking strip isdepicted wherein a first end of wicking strip 30′ has a first height h₁,and a second end a second height h₂, wherein h₁ is less than h₂. Asillustrated in FIG. 5B, the asymmetrical-height wicking strip 30′ may beapplied to the periwound region with the first, shorter end adjacent tothe wound and the second, taller end furthest from the wound. Whenreservoir 40 is compressed onto wicking strip 30′ in this arrangement,wicking strip 30′ will apply a lower pressure adjacent to the wound, dueto the smaller amount of material being compressed, and a higherpressure further from the wound, due to the greater amount of materialbeing compressed in that region. While compressed, wicking strip 30′ mayappear to have the same height along its length, even though itsthickness varies in its native (non-compressed) state. Alternatively, asillustrated in FIG. 5C, wicking strip 30′ may be applied to theperiwound region with the second, taller end adjacent the wound and thefirst, shorter end furthest from the wound. When reservoir 40 iscompressed onto wicking strip 30′ in this arrangement, wicking strip 30′will apply a higher pressure adjacent the wound, due to the greateramount of material being compressed, and a lower pressure further fromthe wound, due to the smaller amount of material being compressed. Thearrangement of such an asymmetrical wicking strip 30′ may be selectedbased on the type of wound being treated. For example, pressure woundsmay benefit from a lower pressure being applied near the wound, whereasvenous leg ulcers may benefit from a higher pressure being applied nearthe wound. Other types of wounds may benefit from different pressuregradients being applied. In many embodiments, wicking strip 30 iscomposed of a supple material that, when pressure is applied to it, doesnot create a potentially harmful pressure ring around the wound.

As illustrated in FIGS. 4 and 5A-5C, the wicking strip may have arelatively even width along its length. However, the wicking strip ofthe present invention also may be provided in a variety of other shapesand sizes, depending on the intended application. FIG. 6A illustrates anembodiment in which wicking strip 30″ is additionally provided withrelaxation cuts 33 that enhance its lateral flexibility, therebyfacilitating lateral bending without buckling or crimping. Non-stickliner 34 is attached to layer 25 of adhesive, and may include tabs 35that facilitate application of the wicking strip.

FIG. 6B illustrates an embodiment in which wicking strip 30′″ ispre-formed in a bowed or arcuate shape, optionally including widerthicker portion 36, which may facilitate application of the wickingstrip around the wound by reducing the lateral bending required tosurround the wound. The degree to which wicking strip 30′″ is bowed mayvary, depending on the size of the wound with which it is intended to beused, and the compliance of the material. For example, wicking strip30′″ may be highly bowed, e.g., formed to be a spiral in its nativeconfiguration (before adhesion to the epidermis). FIG. 6B alsoillustrates tabs 35, which are part of or attached to non-stick liner 34and may facilitate removal of the liner, which may optionally beincluded in any embodiment of wicking strip 30.

In still other embodiments (not illustrated), the wicking strip ispre-formed into an annular form. If the inner boundary of such anannular form does not come sufficiently close to the border of the woundto protect the periwound region, then additional pieces of wicking stripmay be applied in the gap between the annular form and the margin of thewound.

Reservoir 40

As illustrated in FIG. 1, reservoir 40 may include multiple layersbonded together or alternatively may be formed of a single, hydrophiliclayer. In the embodiment of FIG. 1, reservoir 40 includes upper layer41, lower layer 42 and intervening layer 43. Lower layer 42 engages theupper surfaces of wicking strip 30, and transfers exudate throughintervening layer 43, and into upper layer 41. Although reservoir 40 iscomposed of breathable material that allows for the transfer of moisturevapor as needed, reservoir 40 optionally may contain vent 44 thatextends through the reservoir to provide a less impeded route formoisture vapor transfer.

Referring again to FIG. 1B, both upper layer 41 and lower layer 42 arehydrophilic. However, layers 41 and 42 may have the same or differenthydrophilicities, mechanical properties, transfer rates for exudate, andcapacities for absorbing exudate. In some embodiments, layers 41 and 42are formed from hydrophilic polyurethane foams, e.g., commerciallypurchased polyurethane foams from Rynel, Inc. (Wicasset, Me., USA). Thefoam from which lower layer 42 is fabricated has a higher hydrophilicitythan that of upper layer 41, allowing it to rapidly transfer exudateinto upper layer 41. The polyurethane foams may be coated or interlacedwith any suitable antibacterial or antimicrobial agents (e.g., silver)to combat or prevent infection.

Intervening layer 43 enhances the strength and stiffness of reservoir40, making it more difficult to inadvertently deflect reservoir 40downward to contact the wound. Intervening layer 43 may be, for example,a substantially non-stretchable mesh or scrim, such as a metallic,nylon, or polyester-based mesh.

In some embodiments, layers 41, 42, and 43 are co-selected to enablereservoir 40 to form a dome-like shape as it absorbs exudate and swells,while still maintaining contact with ledge 23 and sidewall 21 of supportcushion 20. For example, intervening layer 43 may be formed to have alarger diameter than the diameter defined by the sidewall 21 of supportcushion 20. As reservoir 40 absorbs exudate and swells, this differencein diameter allows intervening layer 43 to buckle upward.

Cover 50

Referring now to FIGS. 1B and 7, cover 50 is described havingpre-fastened reservoir 40 with vent 44. Cover 50 may be adhered to upperlayer 41 with a layer of adhesive, or otherwise attached to upper layer41 before or after reservoir 40 is placed over the wound. During use,cover 50 is adhered to sidewall 21 using layer 27 of adhesive, whichurges reservoir 40 against wicking strip 30. In some embodiments, cover50 extends beyond the lateral dimensions of support cushion 20, so thatwhen dressing 10 is applied to a patient, cover 50 drapes over supportcushion 20 and covers layer 27 of adhesive. Such draping protects theedges of support cushion 20 from lifting, and additionally provides asmooth, comfortable surface over which clothing and bed linens may slidefreely. In other embodiments, layer 27 may comprise a removablefastener, such as a hook and pile arrangement that enables the cover tobe periodically removed to inspect the wound, apply medicaments, or toreplace the wicking strip or reservoir.

Cover 50 is made of a soft, occlusive material that provides anantibacterial barrier between the wound and the environment, and alsoallows humidity to escape from reservoir 40 and vent 44. One example ofa suitable material for cover 50 is Intelicoat 2327, available fromIntelicoat Technologies (South Hadley, Mass., USA). The material may becoated or intercalated with any suitable antibacterial or antimicrobialagent to combat or prevent infection.

ADDITIONAL ALTERNATIVE EMBODIMENTS

Referring now to FIGS. 8 and 9, additional embodiments of the supportcushion and wicking strips suitable for use in the dressing of thepresent invention are described, which simplify the construction andapplication of the dressings. In FIG. 8, support cushion 70 comprisessidewall 71 of uniform height defining opening 72 and wicking strip 80disposed within opening 72. The upper surface of wicking strip 80visible in FIG. 8 is recessed below the top of sidewall 71 of supportcushion 70 to accept reservoir 40 and cover 50 as described with respectto preceding embodiments. Preferably, the height of wicking strip 80 isin a range of 40-60% of the height of sidewall 71. In this embodiment,wicking strip 80 is pre-adhered to support cushion 70 so that the lowersurfaces of support cushion 70 and wicking strip 80 are flush, andincludes opening 81 that may be used to visually position the unit overa wound. Wicking strip 80 includes spiral perforation 82 that extendsthrough the height of the wicking strip, so that the perforation formsspiraled inner portion 83 of the wicking strip. The innermost end of thespiraled portion terminates at pull tab 84.

Support cushion 70 and wicking strip 80 preferably include a layer ofadhesive on the lower surface, similar to layer 25 in the embodiment ofFIG. 1B, which is covered by non-stick liner having removal tab 85.Support cushion 70 also includes layer 27 of adhesive or other suitablefastening means on its upper surface, and may include a plurality ofslits 28, as described for preceding embodiments, to improvebreathability and conformability of the support cushion. Reservoir 40and cover 50, as described for preceding embodiments, may be employed,so that the reservoir fits snugly within the recess above wicking strip80.

In the embodiment of the invention depicted in FIG. 8, spiraled portion83 of wicking strip 80 is configured to be removed, using pull tab 84,to unwind the wicking strip to just expose the margin of the wound. Thelength of the spiraled portion 83 that is unwound to expose the marginof the wound then is cut off with a scissor and discarded. In thismanner, the wicking strip may be easily positioned at the preferredlocation at the margin of the wound, with the remainder of wicking strip80 covering the periwound region, thereby reducing the time required toapply the inventive dressing. Once the support cushion and wicking stripare positioned, and the appropriate length of spiraled portion 83removed to expose the margin of the wound, the reservoir and cover thenis fastened atop support cushion 70 and wicking strip 80 so that thereservoir is engaged with the upper surface of wicking strip 80.

In the embodiment of FIG. 9, support cushion 90 is configured similar tosupport cushion 70 of FIG. 8, and includes sidewall 91 of uniform heightthat defines opening 92. Wicking strip 100 is disposed within opening 92so that its upper surface is recessed below the top of sidewall 91 toaccept reservoir 40 and cover 50 as described with respect to precedingembodiments. Preferably, the height of wicking strip 100 is in a rangeof 40-60% of the height of sidewall 91 and is pre-adhered to supportcushion 90 so that the lower surfaces of support cushion 90 and wickingstrip 100 are flush. Wicking strip 100 includes opening 101 that may beused to visually position the unit over a wound, plurality of circularperforations 102 and illustratively, four radially-directed perforations103 that divide the wicking strip into quadrants. Pull tabs 104 areconnected to the innermost ring of the wicking strip in each quadrant.Perforations 102 and 103 extend through the height of the wicking strip,so that the perforations form arcs of predetermined length 105 that maybe individually removed using pull tabs 104.

Support cushion 90 and wicking strip 100 preferably include a layer ofadhesive on the lower surface, similar to layer 25 in the embodiment ofFIG. 1B, which is covered by non-stick liner having removal tab 106.Support cushion 90 also includes a layer of adhesive or other suitablefastening means on its upper surface, and may include a plurality ofslits, as described for preceding embodiments, to improve breathabilityand conformability of the support cushion. Reservoir 40 and cover 50, asdescribed for preceding embodiments, may be employed.

In the embodiment of the invention depicted in FIG. 9, arcs 105 ofwicking strip 100 are configured to be removed, using pull tabs 104, toremove the portion of the wicking strip up to the margin of the wound.Thus, the patient or caregiver would first remove the non-stick linerfrom the support cushion and wicking strip, and align it centered on thewound using opening 101. The patient or caregiver then would remove aselected, and perhaps unequal, number of arcs 105 from each quadrantusing pull tabs to best approximate, or slightly overlap, the margin ofthe wound. The removed arcs 105 of wicking strip 105 then may bediscarded. Once the support cushion and wicking strip are so applied, areservoir and cover, as described for preceding embodiments, is fastenedatop support cushion 90 and wicking strip 100 so that the reservoir isengaged with the upper surface of the wicking strip.

It should be understood that the dressing of FIG. 9 advantageouslypermits an uneven number of selected arcs 105 of the wicking strip to beremoved from each quadrant, thereby enabling the patient or caregiver tobest approximate irregularities in the margin of the wound. This in turnprovides a high degree of protection of the periwound region, withoutthe need to custom fit the entire length of the wicking strip to coverthe periwound region between the support cushion and the margin of thewound, for example, as described with respect to FIG. 4. In addition, itshould be understood that while the wicking strip 100 of the embodimentof FIG. 9 includes four radially-directed perforations, a greater orlesser number of such perforations may be provided, and that sectorsdefined by such perforations need not encompass equal areas.

Referring now to FIG. 10, a further alternative embodiment of thedressing of the present invention is described which provides theability to periodically apply medications or to lavage wound W inepidermis E without disassembling dressing 110. Dressing 110 includessupport cushion 111, a wicking strip as described with respect topreceding embodiments (omitted for clarity in FIG. 10), reservoir 112and cover 113. The support cushion, wicking strip, reservoir and coverare constructed substantially as described for preceding embodiments.Dressing 110 differs from preceding embodiments in that support cushion111 includes flexible tube 114 that may be permanently or removablyinserted through the sidewall of the support cushion to deliver fluids,such as topical antibiotics or washing fluids through the sidewall towound W, without needing to remove the reservoir and cover. Syringe 115may be selectively coupled to the distal end of tube 114 to injectfluids into dressing 110.

In addition, because the dressing of the present invention, whenassembled and applied to a patient, provides an essentially closedsystem (other than by permitting excess humidity to dissipate throughthe breathable cover), it is also possible for a dressing constructed inaccordance with the present invention to be employed in negativepressure wound therapy. For example, rather than using syringe 115 inthe embodiment of FIG. 10 to inject fluids into the dressing, by pullingthe piston of an empty syringe, the syringe could be used to create anegative pressure environment in the wound environment. Alternatively,instead of the syringe 115, tube 114 instead may be connected to aconventional squeeze ball/valve arrangement or low-pressure vacuum pumpto partially evacuate the dressing. In this manner, the patient orcaregiver may periodically reduce the pressure within the compartmentformed by dressing 110 to promote exudate flow, and speed the healingprocess.

With respect to FIG. 11, an alternative design of a dressing inaccordance with the principles of the present invention is described.Dressing 120 includes support cushion 121, a wicking strip as describedwith respect to preceding embodiments (again omitted for clarity),reservoir 122 and cover 123. The support cushion, wicking strip,reservoir and cover are constructed substantially as described forpreceding embodiments. Dressing 120 differs from preceding embodimentsin that cover 123 includes bellows 124 that communicates with the ventthat passes through the reservoir (see vent 44 in FIG. 1B). Bellows 124preferably comprises a light-weight plastic or synthetic rubber andincludes one-way valve 125, so that depressing bellows 124 induces anegative pressure within dressing 120. As for previously-describedembodiments, cover 123 preferably comprises a breathable material thatpermits excess humidity to be released from within dressing, but issufficiently air-tight to retain a negative pressure induced within thedressing by bellows 124 for an appropriate amount of time, e.g., 5-10minutes, to stimulate exudate flow. In this manner, the patient orcaregiver may periodically reduce the pressure within the compartmentformed by dressing 120 by depressing bellows 124, thereby speeding thehealing process with reduced or no pain or discomfort to the patient.

Referring now to FIGS. 12A and 12B, a further alternative embodiment ofa wound dressing constructed in accordance with the principles of thepresent invention is described. As for the embodiment of FIG. 1,dressing 130 includes three discrete components that are assembled andapplied over wound W on patient's epidermis E. In particular, dressing130 includes support cushion 131, wicking strip 132, and reservoir 133,which may be pre-attached to cover 134. Preferably, components 131-134are sized for use with one another and are enclosed in a sterile packagewith suitable instructions to enable the patient or caregiver to quicklyand accurately apply the dressing.

Support cushion 131 preferably comprises a closed cell polyolefin foamand is designed to surround wound W and periwound region P, i.e., theregion of epidermis E extending from the wound margin, to protect thewound and elevate reservoir 133 and cover 134 above the wound bed. Inthe embodiment of FIG. 12, support cushion 131 has a uniform height, sothat reservoir 133 is supported directly by the upper surface of supportcushion 131, as depicted in FIG. 12B. As for preceding embodiments, thelower surface of support cushion 131 includes a layer of biocompatibleadhesive, which preferably is hydrophobic and breathable. Supportcushion 131 preferably includes slits or perforations 135 that extendthrough the height of the support cushion to facilitate the escape ofperspiration from beneath the support cushion when is it fastened toepidermis E. Support cushion 131 includes opening 136 that exposes aportion of the periwound region extending away from the margin of woundW, to permit placement of wicking strip 132, as depicted in FIG. 12B. Asnoted above, support cushion may comprise a breathable open weave spacerfabric instead of a closed cell polyolefin foam.

Wicking strip 132, which preferably comprises an open-cell polyurethanefoam, overlays periwound region P between the margin of wound W andopening 136 of support cushion 131. In the embodiment of FIG. 12,wicking strip 132 is depicted as a curved strip of foam, although it maytake other forms as described with respect to FIGS. 5 and 6. Wickingstrip 132 preferably includes a layer of biocompatible adhesive, whichpreferably is hydrophobic and breathable, on its lower surface to adhereto the patient's epidermis. During application, wicking strip 132 fitswithin opening 136 of support cushion 131, so that the innermost edge ofthe wicking strip preferably overlaps the margin of the wound by 1-2 mm.For the embodiment of FIG. 12A, wicking strip 132 may be cut with ascissor to ensure that the foam is not overly compressed when adhered tothe periwound region.

Still referring to FIG. 12, reservoir 133 preferably comprises asandwich of different density open cell polyurethane foams, as describedwith respect to the embodiment of FIG. 1, and comprises one or morefoams selected to absorb exudate from wicking strip 132 and to sequesterthe exudate away from the wound bed. Reservoir 133 may be fastened tothe underside of cover 134, and may include a layer of adhesive alongthe perimeter of its lower surface to adhere to the upper surface ofsupport cushion 131. Reservoir 133 includes a hydrophobic gasket 137disposed on its lateral face, as depicted in FIG. 12B, so that exudatedrawn into the reservoir from wicking strip 132 cannot seep out of thelateral face of the reservoir. Gasket 137 may comprise a hydrophobicfilm applied to the exterior lateral surface of reservoir 133.Alternatively, gasket 137 may comprise a closed cell hydrophobic foamadhered to the perimeter of reservoir 132, which is capable ofsupporting a compressive load (like the material of support cushion131). Reservoir 133 is sized so that its outer edges are supported onthe upper surface of the innermost portions of support cushion 131 andwicking strip 132. Reservoir 133 preferably includes one or more vents138 that assist in modulating the humidity within the dressing throughcover 134.

Cover 134 is preferably a breathable material and overlays reservoir133, and includes a layer of adhesive along the circumference of itslower surface that may be used to removably secure reservoir 133 inengagement with epidermis E and to adhere cover 133 to epidermis E. Inaccordance with one aspect of the present invention, cover 134 includesplurality of holes 139 that permit the reservoir and cover to becorrectly aligned with the wicking strip and support cushion duringapplication. In particular, holes 139 permit the caregiver to sightthrough the holes during application of the cover and reservoir toconfirm proper positioning of the cover and reservoir relative tosupport cushion 131.

As illustrated in FIG. 12B (from which cover 134 has been omitted forclarity), during use of dressing 130, exudate EX flows out of wound W ata flow rate that depends on many factors, including the pressure withwhich wicking strip 132 is pressed against the periwound region, thelateral profile of the wicking strip as described above with referenceto FIGS. 5A-5C, the characteristics of wound W, and the consistency ofthe exudate. As exudate EX is released from the wound, it contacts andis absorbed by wicking strip 132. Wicking strip 132 transports exudateEX laterally (in the plane of epidermis E) and then vertically(perpendicular to the plane of epidermis E) to reservoir 133. Exudatetransported laterally may eventually reach support cushion 131, which isformed of a hydrophobic material, and inhibits further lateral transportof the exudate. Instead, exudate EX is transported vertically fromwicking strip 132 and into reservoir 133, which sequesters exudate awayfrom the wound. Reservoir 133 preferably has a large absorptive surfacearea and the capacity to hold large amounts of exudate, e.g., sufficientcapacity so that reservoir 133 need only be replaced once every fewdays. Additionally, gasket 137 inhibits leakage of exudate ontoperiwound region P. Because Reservoir 133 is constructed of a breathablematerial, the water in the exudate absorbed by reservoir 133 is releasedin the form of vapor V into the atmosphere via breathable cover 134.

Referring now to FIGS. 13A and 13B, an alternative embodiment of areservoir and cover suitable for use with the dressing of the presentinvention is described. In the embodiment of FIG. 1, sidewall 21provides structural support for the reservoir against compressive loadsapplied to the dressing, while gasket 137 of reservoir 133 provides asimilar function in the embodiment of FIG. 12. As described earlier,however, it may be desirable, with an irregularly shaped wound, tocustom-fit a support cushion using a strip. A problem with thisapproach, however, is that if the reservoir is cut to the overall shapeof the wicking strip and support cushion, the gasket or hydrophobic filmat the edge of the reservoir may be removed, and exudate may leak fromthe exposed edge of the reservoir. One solution is to drape the coverover the sides of the cut reservoir, having this approach does notprovide mechanical support to reservoir to resist compressive loads.

One solution to the foregoing concern is construction for the reservoirand cover depicted in FIGS. 13A and 13B. In this embodiment, cover 140includes rigid inverted basket 141 joined along its lower edge toelastomeric adhesive bandage 142. Reservoir 150, which may be similar inconstruction to reservoir 133 of FIG. 12, and includes gasket 137, isdisposed within basket 141. Basket 141 is formed from plurality ofradial struts 143, circumferential struts 144 and vertical struts 145.Struts 143, 144 and 145 preferably are formed from a tough, resilientplastic, such as polyurethane, and protect reservoir 150 fromcompressive loads.

Advantageously, cover 140 and reservoir 150 are preformed in specificsizes, e.g., small, medium and large diameters. During application ofthe inventive dressing to an irregularly shaped wound, the wicking stripand support cushion may be custom-fit from strip-shaped support cushionand wicking strips by wrapping the support cushion and wicking striparound the wound. A suitably sized cover 140 and reservoir 150 may thenbe selected from the preformed sizes such, when applied, that the outeredge of the reservoir sits atop at least the innermost rings (orspirals) of the support cushion. For example, if the wound is relativelysmall, the reservoir may extend to the outermost ring of the supportcushion. On the other hand, if the wound is large, the reservoir may sitatop the innermost ring of the support cushion. Since for thisembodiment it is not necessary to cut the outer edge of the reservoir,the gasket remains intact and prevents diffusion of exudate through thelateral edges of the reservoir. In addition, the basket providesmechanical support and protection for the reservoir against compressiveloads, thus preventing exudate absorbed into the reservoir from beinginadvertently released into the wound bed.

Kits

The components of a dressing constructed in accordance with theprinciples of the present invention, illustratively dressing 10 of FIG.1, may be provided to patients or caregivers as a kit 160, illustratedin FIG. 14. Kit 160 includes a cardboard or other sturdy, disposablebacking 161 upon which support cushion 20, wicking strip 30, reservoir40, and cover 50 are removably mounted. Examples of alternativedisposables backing 161 are dark, colored or translucent trays ofmaterials such as polystyrenes (for example available from Sealed AirCorp., Elmwood Park, N.J., USA; or Perfecseal®, a BEMIS Co., Oshkosh,Wis., USA). Kit 160 may also include additional components, e.g., extrawicking strips 30, or different sizes and shapes of support cushion 20,to be able to accommodate different sizes and shapes of wounds. In analternative embodiment, the components of dressing 10 are insteadprovided in one or more compartments of a tray.

In the illustrated embodiment, foldable tabs 162 cut from backing 161and/or pieces of excess material adhered to backing 161 may be used tosecure the components of dressing 10 to backing 161 until they areneeded. For example, the hole in support cushion 20 may be formed bycutting piece 163 from a layer of flange material, and then adheringthat piece 163 to backing 161. Because piece 163 snugly fits into thehole of support cushion 20, the friction between piece 163 and supportcushion 20 serves to removably retain support cushion 20 on backing 161without the need for additional adhesive or tabs, until removed by thepatient or caregiver. Similarly, reservoir 40 may be cut from the centerof a larger piece 164 that is subsequently adhered to backing 161.Friction between reservoir 40 and piece 164 retains reservoir 40frictionally engaged on backing 161 without the need for additionaladhesive or tabs, until removed for use. Alternatively, tabs 162 may beused to secure all of the components onto backing 161.

Instructions for use 165 for applying the different components ofdressing 10 to a patient may be printed on backing 161, e.g.,instructions for implementing the method described with respect to FIG.3. The instructions may be sterilized so that they may be safely used ina sterilized field, such as an operating room. The adhesive layers onthe different components are covered with non-stick, removable linersthat may be color coded to guide the patient or caregiver in determiningthe order in which to apply the components of dressing 10. Suchnon-stick liners may facilitate handling of the different components ofdressing 10, e.g., while placing support cushion 20 on the patient'sepidermis.

Kit 160 preferably further includes a pouch (not shown) in which backing161 and dressing 10 are sealed until needed. Preferably, the pouch istransparent on at least its upper surface, allowing backing 161 and theother components to be viewed. Additionally, instructions for use 165may be located on backing 161 so as to make possible reading of theinstructions before opening the pouch. The pouch also may be constructedto aid retention of the components of dressing 10 on backing 161. Kit160 preferably is sterilizable, e.g., may be sterilized after assembly,such that the contents of the pouch remain sterile until it is opened,e.g., immediately before the dressing is applied to a patient. The pouchpreferably comprises a material that retains its integrity duringconventional sterilizing procedures, e.g., exposure to gamma radiation,to an electron beam, or to ethylene oxide gas.

It is envisioned that a typical wound care treatment environment, suchas a hospital, wound care outpatient clinic or doctor's office, maystock an inventory of kits 160 designed for use with different sizes orshapes of wounds. For example, a plurality of kits 160 may bemanufactured having support cushion 20, wicking strip 30, reservoir 40,and cover 50 in a variety of sizes and shapes, according to differentwound sizes and shapes with which they may be suitable for use.Alternatively, or in addition, individual components of the dressing,such as the wicking strips and reservoirs, may be individually packaged,for example to permit periodic replacement of the wicking strip orreservoir with greater frequency than the dressing as a whole. As astill further alternative, as described above, the wicking strip andsupport cushion may be individually packaged in a roll form, so that thedressing may be applied in a custom-fit manner, while cover andreservoir combinations, such as described above with respect to FIG. 13,may be made available in discrete sizes, so that the dressing may beapplied to a wide range of wound topologies.

INCORPORATED REFERENCES

The following commonly-owned patent publications describe additionalmaterials and structures that may be used in various embodiments of theinvention, and are each incorporated by reference herein in theirentireties:

-   U.S. Patent Publication No. 2006/0235347;-   U.S. Patent Publication No. 2007/0142757;-   U.S. Patent Publication No. 2007/0142761;-   U.S. Patent Publication No. 2007/0161937;-   U.S. Patent Publication No. 2007/0161938; and-   U.S. Patent Publication No. 2007/0191754.

While various illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true spirit and scope of theinvention.

1. A dressing for protecting a wound and managing exudate released fromthe wound, the wound having a margin and being surrounded by a periwoundregion, the dressing comprising: a support cushion configured tosurround the wound and the periwound region; a wicking strip configuredto be positioned immediately adjacent the margin of the wound in theperiwound region between the support cushion and the margin of the woundand independently of the support cushion such that the wicking stripwicks the exudate from the margin of the wound and substantiallyinhibits contact between the exudate and the periwound region; and areservoir configured to be suspended over and in engagement with thewicking strip so that the wicking strip transfers exudate from the woundto the reservoir; and a cover configured to be positioned over thereservoir.
 2. The dressing of claim 1, wherein the cover is configuredto retain the reservoir in engagement with the wicking strip.
 3. Thedressing of claim 1, wherein the support cushion further comprises asidewall and a flange, the flange defining a ledge to accept a portionof the reservoir.
 4. The dressing of claim 3, wherein the supportcushion comprises a hydrophobic material, the wicking strip and thereservoir comprise hydrophilic materials, and the sidewall, ledge andflange inhibit seepage of exudate out of the reservoir and wicking striponto the periwound region.
 5. The dressing of claim 1, wherein aplurality of slits are disposed in the support cushion.
 6. The dressingof claim 1, wherein the wicking strip has a length and a height, and theheight varies along the length such that engagement of the reservoir tothe wicking strip induces a pressure gradient in the periwound region.7. The dressing of claim 1, wherein the reservoir comprises a firsthydrophilic layer, a non-stretchable mesh or scrim, and a secondhydrophilic layer.
 8. The dressing of claim 1, wherein the covercomprises a breathable material.
 9. The dressing of claim 8, wherein avent is defined in the reservoir, the vent permitting humidity over thewound to escape.
 10. The dressing of claim 1, wherein the supportcushion further comprises a tube that enables fluids to be injected intothe dressing without removing the reservoir or cover.
 11. The dressingof claim 1, wherein the cover further comprises a bellows configured tobe depressed to periodically induce a negative pressure within thedressing.
 12. A method for protecting a wound and managing exudatereleased from the wound, the wound having a margin surrounded by aperiwound region, the method comprising: surrounding the wound and theperiwound region with a support cushion; applying a wicking stripimmediately adjacent the margin of the wound in the periwound regionbetween the support cushion and the margin of the wound andindependently of the support cushion such that the wicking strip wicksthe exudate from the margin of the wound and substantially inhibitscontact between the exudate and the periwound region; and applying areservoir over the wicking strip, wherein the wicking strip transfersexudate from the wound to the reservoir.
 13. The method of claim 12,further comprising substantially filling the periwound region betweenthe support cushion and the margin of the wound with the wicking strip.14. The method of claim 12, wherein the support cushion includes astepped profile that defines a ledge and a recess, the method furthercomprising fitting the reservoir within the recess so that the reservoirengages the ledge and is suspended over the wound.
 15. The method ofclaim 14, wherein the support cushion comprises a hydrophobic materialand the wicking strip and the reservoir comprise hydrophilic materials,the method further comprising inhibiting lateral flow of exudate out ofthe reservoir or the wicking strip onto the periwound region.
 16. Themethod of claim 15, wherein urging the reservoir into engagement withthe wicking strip further comprises applying a compression wrap over thedressing.
 17. The method of claim 12, further complying stimulatingexudate flow by urging the reservoir into engagement with the wickingstrip to induce pressure in the periwound region.
 18. The method ofclaim 17, wherein the wicking strip has a length and a height and theheight varies along the length, and wherein the method further comprisesapplying the wicking strip in the periwound region to induce a pressuregradient in the periwound region when the reservoir is engaged to thewicking strip.
 19. The method of claim 12, further comprising applying amedication to the wound before applying the reservoir.
 20. A kit for adressing for use in protecting a wound and managing exudate releasedfrom the wound, the wound having a margin surrounded by a periwoundregion, the kit comprising: a support cushion configured to surround thewound and the periwound region; a wicking strip configured forapplication immediately adjacent the margin of the wound in theperiwound region between the support cushion and the margin of the woundand independently of the support cushion such that the wicking stripwicks the exudate from the margin of the wound and substantiallyinhibits contact between the exudate and the periwound region; areservoir configured to be applied over the wicking strip; a backingupon which the support cushion, wicking strip, and reservoir aremounted; and instructions for use printed on the backing, theinstructions for use describing steps for assembling the dressing.